Lysozyme functionalized silver nanoclusters as a dual channel optical sensor for the effective determination of glutathione

This article describes the development of a facile and efficient fluorescence sensor for the determination of glutathione (GSH). Presence of the antioxidant glutathione in blood serum is considered as a biomarker for catastrophe like colorectal cancer. Silver nanoclusters with strong fluorescence and good water solubility synthesized from relatively cheaper precursors are one of the species very much explored in fluorescence sensors and bioimaging. Here, Chicken egg derived-lysozyme functionalized silver nanoclusters (Lyz AgNCs) with red fluorescence emission has been synthesized and developed to a turn-off fluorescence sensor for GSH through which colorimetric determination is also possible. Due to the ground state 'Ag-S' interaction between Lyz AgNCs and GSH, the determination of the analyte is possible from 1.00 × 10-5 M to 1.00 × 10-6 M via fluorimetric and from 9.00 × 10-6 to 8.00 × 10-7 M via spectrophotometric techniques with a limit of detection 2.86 × 10-7 M and 4.76 × 10-7 M, respectively. Selectivity of the sensor has been studied and applicability of the sensor in artificial blood serum samples has been demonstrated.

Fluorescent cellulose nanofibrils-based hydrogel incorporating MIL-125-NH2 for effective adsorption and detection of iodide ion

To remove iodine ion (I-) from wastewater, a novel hydrogel, the fluorescent cellulose nanofibrils-based hydrogel (FCNH), was synthesized to enable both detection and adsorption of I-. The FCNH comprised cellulose nanofibrils (CNs), silver nanoclusters (AgNCs), and MIL-125-NH2. It exhibited an excellent adsorption capacity for I-, with a maximum adsorption capacity of 373.7 mg/g, fitting both the Langmuir and pseudo-second-order models. Additionally, FCNH displayed excellent regeneration properties, retaining 88.0 % of its initial adsorption capacity after six adsorption-desorption cycles. Functioning as a fluorescent sensor, the synthesized FCNH enabled the detection of I- through dynamic quenching, with linear ranges of 5 to 200 mg/L and 0.2 to 1.0 μg/L, and a determination limit of 0.11 μg/L. Analysis of the adsorption and detection mechanisms revealed that FCNH's outstanding performance arose from its 3D porous structure comprising CNs, AgNCs, and MIL-125-NH2. Economic analysis indicated that FCNH was inexpensive compared to commercially available activated carbon. Thus, FCNH demonstrated significant potential as an economical and reusable adsorbent for iodine ion removal.

Luminescent carbon dots versus quantum dots and gold nanoclusters as sensors

Ultra-small nanoparticles, including quantum dots, gold nanoclusters (AuNCs) and carbon dots (CDs), have emerged as a promising class of fluorescent material because of their molecular-like properties and widespread applications in sensing and imaging. However, the fluorescence properties of ultra-small gold nanoparticles (i.e., AuNCs) and CDs are more complicated and well distinguished from conventional quantum dots or organic dye molecules. At this frontier, we highlight recent developments in the fundamental understanding of the fluorescence emission mechanism of these ultra-small nanoparticles. Moreover, this review carefully analyses the underlying principles of ultra-small nanoparticle sensors. We expect that this information on ultra-small nanoparticles will fuel research aimed at achieving precise control over their fluorescence properties and the broadening of their applications.

Current trends in carbon-based quantum dots development from solid wastes and their applications

Urbanization and a massive population boom have immensely increased the solid wastes (SWs) generation and are expected to reach 3.40 billion tons by 2050. In many developed and emerging nations, SWs are prevalent in both major and small cities. As a result, in the current context, the reusability of SWs through various applications has taken on added importance. Carbon-based quantum dots (Cb-QDs) and their many variants are synthesized from SWs in a straightforward and practical method. Cb-QDs are a new type of semiconductor that has attracted the interest of researchers due to their wide range of applications, which include everything from energy storage, chemical sensing, to drug delivery. This review is primarily focused on the conversion of SWs into useful materials, which is an essential aspect of waste management for pollution reduction. In this context, the goal of the current review is to investigate the sustainable synthesis routes of carbon quantum dots (CQDs), graphene quantum dots (GQDs), and graphene oxide quantum dots (GOQDs) from various types SWs. The applications of CQDs, GQDs, and GOQDs in the different areas are also been discussed. Finally, the challenges in implementing the existing synthesis methods and future research directions are highlighted.

Tannic Acid Capped Copper Nanoclusters as a Cost-Effective Fluorescence Probe for Hemoglobin Determination

For the first time, we report on a copper nanoclusters based fluorescence sensor for hemoglobin (Hgb). The aggregation-induced quenching of tannic acid capped copper nanoclusters' (TACuNCs) fluorescence by a Hgb-H₂O₂ mixture that mimics the Fenton's reagent is used here for the selective determination of Hgb. It is possible to effectively determine Hgb using this sensitive and cost-effective sensor in the linear range of 5.0 × 10^-8 to 4.0 × 10^-9 M with a detection limit of 5.6 × 10^-10 M. The practical utility of the sensor is evident from the good recovery values obtained from Hgb spiked with artificial blood serum.

A Simple and Cost Effective Turn off Fluorescence Sensor for Biliverdin and Bilirubin Based on L-Cysteine Modulated Copper Nanoclusters

The present article reports the efficiency of L-cysteine modulated copper nanoclusters (L-cys-CuNCs) as a fluorescent probe for the selective determination of naturally occurring bile pigments biliverdin (BVD) and bilirubin (BLR). These pigments were found to quench the fluorescence of L-cys-CuNCs through static processes. Under optimized conditions, the proposed strategy permitted the quantification of BVD and BLR in the range 4.00 × 10^-5 to 5.00 × 10^-7M and 1.00×10^-5 to 1.00×10^-6 M respectively with limits of detection 2.33 × 10^-7M and 2.29 × 10^-7 M. The practical utility of the developed sensor have been investigated in spiked blood and urine samples.

Interaction of tetracycline with l-cysteine functionalized CdS quantum dots - Fundamentals and sensing application

The present paper reports l-cysteine functionalized CdS quantum dots (QDs) as a simple and highly selective turn-off fluorescence sensor for the determination of tetracycline (TET). The unauthorized use of TET may pose serious health hazards in human beings and hence the detection and determination has become very essential. In this regard, we have developed a sensor that enable the quantification of TET in the range 6.00 × 10^-4 M to 1.50 × 10^-5 M with a limit of detection 7.78 × 10^-6 M, under optimized conditions. Steady state and time resolved fluorescence spectroscopic studies were used for investigating the mechanism of quenching and was found to be a combination of static and dynamic processes. The analytical application of the proposed sensor was investigated in pharmaceutical formulation.

Copper nanoclusters: an efficient fluorescence sensing platform for quinoline yellow

Fluorescence quenching behavior of artificial food colorant quinoline yellow (QY), on interaction with l-cysteine stabilized copper nanoclusters (l-Cys-CuNCs) is investigated in this work. For this purpose, l-cysteine stabilized CuNCs were synthesized and characterized using various analytical techniques. Results demonstrated that the synthesized probe (size ~2 nm) had very promising optical features such as bright blue fluorescence, significant quantum yield and excellent photostability. l-Cys-CuNCs can function as a fluorescence sensor by selectively sensing QY among other yellow colorants, giving a detection limit as low as 0.11 μM. The developed sensor exhibited a linear concentration range from 5.50 to 0.20 μM. The developed fluorescence assay was successfully applied for testing commercial samples, thereby making this sensing strategy significant for quality control of food stuffs.

Supramolecular inter-ionic charge-transfer complexes between derivatives of pyridinium-4-oxime cations and hexacyanoferrate(ii) anions

Mono- and bis-pyridinium-4-oxime compounds are introduced as new electron acceptors for the formation of colored, supramolecular, inter-ionic charge-transfer complexes with hexacyanoferrate(ii) as a donor.